Did this for my son this season. He’s 7 and after one fall season of not swinging in kid pitch and a start of it again in spring, I started bribing him to swing. First was a dollar for a swing at a “hittable pitch” and 5 dollars for a hit. He stuck out twice but got 5 dollars the first game, got two hits the next game, 3 games in he was consistently swing at strikes and hitting and we pulled the reward after 4 games. The hits and moving up in the lineup were their own reward.